Author Topic: color fading  (Read 649 times)

Offline NUViva44

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color fading
« on: October 26, 2017, 09:46:39 PM »
Just a new pi3 and picap. doing some testing to see if anything is wrong. any solid color fill that blends more than one color fades and red eventually dominates the strip. see images. tried on both ports. even tried to skip some channels. no luck. if the strips were either solid red, blue or green there is no fading. not sure if the timings are off somehow. any help would be appreciated.

Offline AAH

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Re: color fading
« Reply #1 on: October 26, 2017, 09:58:12 PM »
What you are seeing is the effect of voltage drop and is the reason for power injection. Any further than 1 strip or about 50 pixels and the voltage level starts to drop to the point where the green and blue leds don't have enough voltage. Red leds run off a lower voltage and stay on for longer. Connecting up 5V or 12V (whichever it is) to the far end of the 2nd strip will fix your problem. Tapping into the junction between the 2 strips will probably fix it as well.

Offline NUViva44

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Re: color fading
« Reply #2 on: October 27, 2017, 08:38:48 AM »
i have run these with a different controller in the past. same power supply same strips. never had a problem like this. is there something about running the power through the picap that might be causing the voltage drop?

Offline AAH

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Re: color fading
« Reply #3 on: October 27, 2017, 05:42:56 PM »
It's a voltage drop issue that occurs with all pixels. The only reasons it could be different with the PiCap is that they are being ran at 100% brightness and potentially they weren't before or alternately there is an excessive voltage drop across the fuse in the PiCap.  To me it looks like these are probably 5m of 5V 2812 pixels which is something like 150 pixels per strip or 300 total. That's about 16.5A total current if my presumptions are correct. This is about the current capacity of the connectors on the PiCap which probably had a 7.5A fuse. But for voltage drop the fuse would probably blow and damage due to overcurrent could be done to the connectors and/or pcb.

Offline NUViva44

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Re: color fading
« Reply #4 on: October 28, 2017, 08:56:12 AM »
ya i must not have been using 100% brightness before. yep you assumed correctly. also using a 300w power supply. would i need to inject power every 50 pixels or could i get away with it somewhere around 75? thanks for all the help!

Offline AAH

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Re: color fading
« Reply #5 on: October 28, 2017, 03:59:13 PM »
It's strip and strip is built to handle a full length without power injection. Tapping into the join between the 2 strips with power may be enough if you use heavy enough cable. If it doesn't sort the issue then tapping in at the join between 2 strips and also the far end will be the go.

 

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